Showing papers by "Felix Schauer published in 2014"

Specific Features of Wendelstein 7-X Structural Analyses

Abstract: The Wendelstein 7-X modular stellarator is in the final assembly phase at the Max Planck Institute for Plasma Physics in Greifswald, Germany. The design and assembly of the basic machine, that is, without in-vessel components, diagnostics and periphery, is completed. Structural parameters such as bolt preload, initial gap widths for contacts between structure elements, final magnet module positions, etc., were specified on the basis of detail numerical modeling and are now implemented. The focus of the numerical analysis has been shifted toward fast consideration of nonconformities and changes in assembly procedures, to preparation of commissioning, assessment of possible field disturbances, and exploration of operational limits. In parallel the analyses of in-vessel components, diagnostics, and periphery are being continued. This paper focuses on the specific features in the development, evolution, and realization of analysis strategies, implemented numerical approaches. Further specific subjects are standards and codes, safety margins in relation to expected tolerances and uncertainties, and the confirmation of analysis results by tests as well as their benchmarking with alternative models in different numerical codes. Finally, some lessons learned so far which might be relevant for other large fusion machines are highlighted, and a brief outlook on future work is given.

Advanced Structural Analysis of Wendelstein 7-X Magnet System Weight Supports

Abstract: TheWendelstein 7-X (W7-X) optimized stellarator is presently under final stage of assembly at theMax-PlanckInstitut für Plasmaphysik in Greifswald. The goal of W7-X is to verify that the advanced stellarator magnetic confinement concept is a viable option for a fusion reactor. The coil system consisting of 70 superconducting coils of seven different types is supported by a massive central support structure (CSS), and thermally protected by the cryostat. The magnet system weight is borne by supports which are bolted to the cold CSS. The CSS is supported by 10 so-called cryo-legs that penetrate through the cryostat wall to the warmmachine base. The design of the cryo-legs incorporates glass-reinforced plastic tubes to guarantee relatively small thermal conductivity for low heat flux to the cryostat. In order to ensure free thermal shrinkage of themagnet system and to reduce stresses in the cryo-legs, sliding and rotating bearings are used as interfaces to the machine base. Tie rods between the machine base and the warm ends of the cryo-legs prevent toroidal movements of the magnet system with respect to the torus axis, as well as a horizontal shift due to any non-symmetric loads. During assembly of the W7-X magnet system some important measurement results have been collected and analyzed. In particular, the assembly of the magnet system introduced some imperfections in the vertical position of the cryo-legs causing considerable additional internal stresses which were not considered during the design stage. In addition, trim coils were installed at a later stage which were not planned originally when the magnet structure was designed. The loads induced by them are not cyclic symmetrical, therefore, the previously used method to analyze one magnet system module with periodical boundary conditions is not applicable. Consequently, a model of the complete magnet system including all five modules was created and analyzed with respect to the mentioned goal. Fatigue analyses of the cryo-legst under the new cyclic loads applied on top of the approximately 100 t static weight has been performed in order to evaluate the life time. The paper presents the progress in structural analyses of the W7-X magnet system under the as-built conditions, loads due to the trim coil operation, and results of the weight support life cycle analysis.